It is well recognized that atherosclerosis is a major medical problem which involves major arteries supplying the heart, the brain and the extremities. It has been possible with the development of ultrasonic techniques to evaluate the location and extent of the involvement in the carotid and peripheral arteries. Since the method is noninvasive, painless and safe, it has been possible to utilize the combination of pulse echo and Doppler methods to assess the degree of narrowing at the time of the examination and to follow changes in the disease during follow-up. It is proposed to further develop these methods to employ the use of computerized pattern recognition which will permit quantification of information present in the Doppler spectrum to predict the degree of stenosis. In addition to providing a more objective assessment of the degree of stenosis, the ultrasonic duplex method will be used to assess the prevalence of restenosis after carotid endarterectomy and its relevance to the development of clinical events such as transient ischemic attacks and strokes.